The present invention relates to a high-vacuum valve that is used to open and close a transfer passage maintained under vacuum and also used to open and close an evacuation passage. To transfer a work such as an integrated circuit (IC) or parts thereof from a vacuum treating chamber to another vacuum treating chamber, for example, a high-vacuum valve is provided in a transfer passage having a rectangular sectional configuration. A high-vacuum valve is also provided in an evacuation passage that connects a high-vacuum treating chamber and a vacuum pump.
There is known a high-vacuum valve for a transfer passage that has a valve body having a valve chamber therein. The valve body has a first opening formed in the front wall thereof and a second opening formed in the rear wall thereof. A valve seat is formed on the inner side of the first or second opening. A valve element (gate or blade) is connected to the proximal end of a valve shaft that performs rectilinear motion. The valve element is pressed against the valve seat to close the valve [for example, see Japanese Patent Application Unexamined Publication (KOKAI) No. 9-303577]. In this high-vacuum valve, the valve shaft extends through a center hole in the top wall of the valve body in a non-contact manner. The side surface of a portion of the valve shaft that is outside the valve chamber is covered with a bellows in a non-contact manner. The area between the distal end of the bellows and the distal end portion of the valve shaft is hermetically sealed. The area between the proximal end of the bellows and a portion of the top wall that surrounds the center hole is hermetically sealed.
In a conventional high-vacuum valve (gate valve) for a transfer passage, after the valve element has been moved to a position facing opposite to the valve seat by the rectilinear motion of the valve shaft, the valve element is pressed against the valve seat by pivotal motion of the valve shaft. In this case, the valve element is pressed against the valve seat by using a complicated mechanism as follows. An engagement portion having a front surface and a rear surface is formed at the distal end of the valve shaft. The front and rear surfaces of the engagement portion are engaged with a first engaging roller and a second engaging roller, respectively, which are rotatably supported by a roller support member. When a fulcrum roller that is connected to the distal end portion of the valve shaft is supported by the proximal end of a fulcrum groove, the roller support member is moved forward to make the first engaging roller engage with a slant portion of the front surface of the engagement portion, thereby causing the valve shaft to pivot in a direction in which the valve element is pressed against the valve seat.
In a conventional high-vacuum valve for an evacuation passage [referred to as "L-type valve"; for example, see Japanese Patent Application Unexamined Publication (KOKAI) No. 10-2452], a reaction product from a reaction gas is deposited on the inside of the high-vacuum valve when the temperature is below a predetermined level, making it difficult to control the high-vacuum valve. To solve this problem, it is required that the upper part of the valve body, the valve-side flange of the valve body, the bellows-side flange of the valve body, the outside of the valve part and so forth should be placed at a uniform temperature. Therefore, to maintain the temperature of the high-vacuum valve for an evacuation passage above a predetermined level, a heater is installed outside the valve body, and materials of high thermal conductivity are used for the valve body, the bonnet, the valve element and the bellows, thereby transferring heat to the inside of the valve body mainly by heat conduction and radiation.